In a typical database system supporting SQL (Structured Query Language), table entries or rows can include one or more fields that are user defined type (UDT) fields. One type of UDT is a UDT structured type. The UDT structured type shares many properties in common with the C-language “struct.” Both a C-language struct and a UDT structured type can be declared to be composed of any number of data members which can be either homogeneous or heterogeneous with respect to their data types. Both a C-language struct and a UDT structured type can also be nested, containing data members which are themselves structured types. The declaration of a UDT structured type is entered into the DBS system using SQL Data Definition Directives.
Typically, a UDT has one or more user defined methods (UDM). In addition, some databases provide user defined functions (UDF) independent of UDT's or allows users to define LDF's directly. Often UDF's or UDM's are used in expressions and the database system executes the UDF's and UDM's in an expression in a serial fashion. For complex and large data types and complex UDF's and UDM's, serial execution may be slow.